Such a method proceeds, for example, from WO 96/39721. The invention is also directed to the employment of such a method. In particular, cuprates on the basis of the bismuth material system Bi-Semiconductor-Ca--Cu--O are included among known superconductive metal oxide compounds having high transition temperatures T.sub.c of at least 77 K, which are therefore also known as high T.sub.c superconductor materials (abbreviated: HTS materials) and enable a cooling by liquid nitrogen (LN.sub.2), whereby individual constituents of this material system can be at least partially replaced by others. In particular, a corresponding partial substitution of the Bi constituent by Pb is possible. At least two superconductive phases occur within this Bi-containing material system, this differing on the basis of the number of copper-oxygen lattice planes (layers) within their crystalline unit cells. A superconductive phase having the approximate composition Bi.sub.2 Sr.sub.2 CaCu.sub.2 O.sub.8+y has a transition temperature T.sub.c of approximately 85 K (what is referred to as 2-layer or what is referred to as 85 K or 2212 phase), whereas the transition temperature of a superconductive phase with the approximate composition Bi.sub.2 Sr.sub.2 Ca.sub.2 Cu.sub.3 O.sub.10+x lies at about 110 K (what is referred to as 3-layer or what is referred to as 110 K or 2223 phase). This latter phase is particularly stabilized by a partial substitution of the Bi by Pb.
Attempts are made with these HTS materials to manufacture elongated superconductors in wire or ribbon form. A method considered suitable therefor is what is referred to as the "powder-in-tube technique" that is fundamentally known from the manufacture of superconductors with the classic metallic superconductor material Nb.sub.3 Sn. According to this technique, a predetermined powder is also introduced into a tubular carrier or, respectively, into a matrix of normally conductive material of, in particular, Ag or an Ag alloy for manufacturing conductors with the aforementioned HTS material. This powder is composed of a fabricated material of the HTS material or contains this material, which generally does not yet exhibit or only slightly exhibits the desired superconductive T.sub.c phase or a phase with lower transition temperature such as, in particular, the 2212 phase.
The structure obtained in this way is subsequently compacted and brought to a desired dimension with shaping steps that can be potentially interrupted by a least one thermal treatment step. Subsequently, the wire-shaped or ribbon-shaped intermediate conductor product obtained in this way is subject to a final annealing for setting or optimizing its superconductor properties or, respectively, for forming the desired high T.sub.c phase, this final annealing being at least partially implemented in an oxygen-containing atmosphere, for example in air (see, for example, Supercond. Sci. Technol., Vol. 4, 1991, pages 165-171 or Vol. 5, 1992, pages 591-598). This final annealing can also be implemented in a plurality of steps or, respectively, at several temperatures, whereby further shaping treatments can also be interposed for forming the ultimate dimension of the final conductor product. According to WO 96/19417, a final annealing with periodically fluctuating temperature management is also possible. Given the method to be derived from the initially cited WO 96/39721, the temperature level in the final annealing is successively lowered from higher to lower temperatures.
When, in a way known in and of itself, a plurality of corresponding ribbon-shaped or wire-shaped high T.sub.c superconductors or their intermediate or conductor products or pre-products are bundled, conductors having a plurality of superconductor cores, what are referred to as multi-core or multi-filament conductors, can also be obtained (see, for example, IEEE Trans. Appl. Supercond., Vol. 5, No. 2, June 1995, pages 1145-1149).
The annealing of the intermediate conductor product in the manufacture of an HTS conductor on the basis of a bismuth cuprate with a phase of the 2223 type is generally implemented given a constant partial oxygen pressure. Work is thereby often carried out with a reduced partial oxygen pressure, whereby the oxygen part of a corresponding atmosphere lies at approximately 8 volume %, and a pressure of the overall atmosphere of approximately 760 Torr (=1013 mbar=1 atm) forms the basis. It has been shown, however, that the proportion of the 2223 phase of the Bi cuprate that forms is comparatively slight. For this reason, attempts have been made to anneal in an atmosphere with a high partial oxygen pressure. A comparatively high proportion of the 2223 phase can then in fact be achieved; the process-engineering outlay for this, however, is comparatively high and the ultimate conductor products nonetheless only have an unsatisfactory critical current density or, respectively, current-carrying capability.
Given the method derivable from WO 96/39721, the intermediate conductor product contains a fabricated material of the superconductor material that comprises a high proportion of a tetragonal or orthorhombic 2212 phase. This intermediate is then subjected to what is referred to as a thermo-mechanical treatment before a final annealing ensues. This thermo-mechanical treatment can comprise a succession of flat processing steps that are interrupted by intermediate annealing steps. The annealing steps should be implemented in an identical atmosphere given an O.sub.2 pressure in the range between 10.sup.-5 and 0.04 atm O.sub.2. The conversion of the orthorhombic 2212 phase into the desired 2223 phase should then ensue with the terminating annealing step of the final annealing, which is implemented given comparatively higher O.sub.2 partial pressure in an atmosphere with 0.003 through 0.21 atm O.sub.2. The cooling process following thereupon should be implemented in an atmosphere with constant O.sub.2 partial pressure.